The viral vector core will provide a variety of vectors, such as adeno- associated viral vector, adenovirus, Moloney murine leukemia viral vector (MoMLV) and lentiviral vector for the various phases of the experiments in this program project. It will assist investigators in designing and constructing recombinant viral vectors and provide large- scale production of recombinant viruses for in vitro and in vivo experiments. The Core will also provide investigators with detailed vector information and sequences. Examples of some of the vectors that will be provided as MFG based retroviral vectors, containing full length EpoR (fEpoR) followed by IRESGFP and vectors containing truncated EpoRs (tEpoR) followed by IRESYFP. The MFGfEpoR-IRESGFP and MFGtEpoR-IRESYFP vectors will be available to researchers in this program project. The viruses will be packaged into PG13 cell lines, containing MoMLV gag-pol proteins and the Gibbon Ape Leukemia Virus env protein than can provide high titer retroviral vectors with an extended host range. This core will also make lentiviral vectors which promote the efficient transfer and suspended expression of gamma-globin genes. A high titer beta- and gamma-globin construct under the control of the micro LCR will be available to researchers in this program project and a newer vector expressing human gamma-globin, which can be distinguished from fetal monkey endogenous gamma-globin will be available to the investigators in this program project. These viruses will be made by co-transfecting 293T cells with the vectors, pCMV8.2, providing lentiviral gag-pol proteins and pMD.G, providing VSV-G pseudotyped env protein. The viruses are subjected to concentration by ultracentrifugation.